Studies in our laboratory focus on the nature of DNA repair mechanisms in the complex eucaryote, Drosophila melanogaster. Procedures for the isolation of mutagen-sensitive mutations have been devised and neary fifty such mutations have been isolated. Complementation analysis of these mutations have indicated a complex pattern of mutagens have indicated a complex pattern of mutagen sensitivity and has led to the formulation of a working model for DNA repair in this organism. Evaluation of these mutant strains as possible tester strains for environmental mutagens and carcinogens is currently in progress.